I. Field of the Invention
The present invention relates generally to transdermal dosage forms for administering substances of a class typically subject to abuse to the body of a patient and, particularly, to reducing the potential, for abuse related to the use of such devices. More particularly, the invention involves the use of binding agents to immobilize and prevent extraction of amounts of abusable substances remaining in transdermal patch devices after initial therapeutic transdermal administration to a patient. Other techniques are also included.
II. Related Art
The temptation and potential for abuse by ingestion, injection, etc. of narcotics and other controlled substances is well known. This widespread abuse issue is exemplified by the problems associated with fentanyl, the widely used potent synthetic narcotic drug. Abuse of this drug has become a significant issue among anesthesiologists and other hospital workers.
Of particular interest is the potential for abuse associated with transdermal patch technology (passive or active) which is a preferred method of administration because it can eliminate the need for repeated oral dosing. Unfortunately, with transdermal patches, significant amounts of drug compound remain in the patches after patients have worn them for the prescribed period of time. The need for this excess amount of drug is well known, it is required to insure an adequate driving force in the transdermal application for the full wear time period. For example, a published test of Duragesic (trademark of Johnson & Johnson) patches worn for the full 72-hour wear period, 28-84.4% of the original loading of fentanyl still remained in the patches. The authors of the study concluded that the residual dosage represented amounts sufficient for abuse and misuse and was even potentially lethal. (Marquardt et al, Ann Pharmacother, 1995, 29:969-71). Using the 2002 published consumption rate of fentanyl, an estimated 50 million or more abusable, toxic dosages of fentanyl are released into the environment annually.
Upon recognizing the need to deactivate residual fentanyl following the wearing of transdermal patches, researchers in a published study recommended that used patches be immersed in heated concentrated hydrochloric or sulfuric acid (Zambaux et. al. Ann Pharm Fr 2000, 58: 176-179). This method was found to deactivate the residual fentanyl by a hydrolysis chemical reaction. A significant disadvantage of this method is that it requires very hazardous materials and procedures.
Another approach to the reduction of abuse potential in transdermal drug administration is found in U.S. Pat. No. 5,236,714. That document discloses the combination of the drug with a co-formulated antagonist agent that is present in a form not releasable in the dosage form, but one which releases to prevent abuse of the composition by certain other routes of administration. Thus, the co-formulated antagonist does not penetrate transdermally, but would be co-extracted during an attempt to extract the abusable material as by using solvents or by removing and ingesting the combination. One disadvantage to this approach resides in the shelf-life complications associated with co-formulation of two active pharmaceutical ingredients in a transdermal patch. Another significant limitation to this approach is that a used patch can still be abused with transdermal wear.
There still remains a need, then, for a safe and effective means of preventing abuse involving excess amounts of drugs, particularly opioid-type drugs associated with transdermal administration of such materials that protects against abuse by transdermal wear without requiring hazardous materials.